Determination of permeability of soils using the multiple piezo-element penetrometer

Abstract

The current method of determining the hydraulic properties of soils using piezocone penetration test (PCPT) requires the advancement of the piezocone penetrometer to the desired depth and holding (or arresting) it for the dissipation test. In order to obtain the hydraulic properties, one analyses the pore water dissipation test results by two-dimensional or three-dimensional radial drainage consolidation. This conventional procedure is methodologically simple and presents relatively reliable values of permeability compared to other field test methods. However, it is still challenging for field engineers and needs to be improved. The piezocone penetrometer intrudes into the ground with the speed of 2 cm/s. Thus, the test mechanism is a kind of strain-controlled condition with partial drainage. Therefore, the excess pore pressure during the piezocone penetration is a function of the permeability of the soil as well as the stress–strain parameters. Thus, with the proper coupled theory of mixtures which can take into account the coupling of solid and pore water flow, one can predict the permeability of the soil from the pore pressure response during PCPT. In this study, the coupled theory of mixtures of the soil grains and the pore water is used in order to predict the permeability of the soil from the excess pore pressure generated from the multiple piezo-element PCPT ‘on the fly’. An elasto-plastic, finite strain constitutive equation in an updated Lagrangian reference frame is used in this work. Using the proposed method, a reliable value of the permeability of soil is obtained conveniently without the use of the pore pressure dissipation tests. Copyright © 1999 John Wiley & Sons, Ltd